In an image forming apparatus of an electro-photograph manner, an electrostatic latent image is formed on a surface of a photosensitive drum and toner that is developer is supplied to the electrostatic latent image on the photosensitive drum from a developing apparatus in which the toner is accommodated, so that a toner image is formed on the surface of the photosensitive drum. The toner image is transferred on a sheet, which is a transfer medium, so that an image is formed on the sheet.
As disclosed in Patent Document 1, the developing apparatus includes a housing having an opening that is opened toward the photosensitive drum, a developing roller that is rotatably supported to the housing and is arranged so that a circumferential surface thereof is exposed from the opening, a toner accommodating chamber in which toner is accommodated, a layer thickness regulating blade that regulates a thickness of a toner layer on the developing roller and a side seal member that prevents toner from being leaked from both end portions of a rotational axis line direction of the developing roller in the opening.
Furthermore, the layer thickness regulating member is configured by a stainless plate spring extending along the circumferential surface of the developing roller and has a leading end portion that is convexly bent to the circumferential surface of the developing roller.
In the meantime, the side seal member has a downstream-side side seal member that is arranged downstream of a rotational direction of the developing roller and an upstream-side side seal member that is arranged upstream of the rotational direction of the developing roller and sandwiches leading end portions of both ends of the layer thickness regulating blade by the downstream-side side seal member and the upstream-side side seal member.    [Patent Document 1] JP-A-2001-209247